The present invention relates to assemblies for performing surgery and particularly to tissue cutters for surgery having concentric cannulas with tip ends configured to allow cutting. Such cutters are particularly applicable for minimally invasive surgical techniques. More particularly, the present invention relates to an improved movable cutting cannula of sufficient size to allow the passage therethrough of tissue specimens or surgical instruments wherein one cannula is movable relative to another cannula to cut tissue.
Removal of tissue from a patient's body for disposal or analysis is commonly required in surgical procedures. Typically, cutting instruments have been used to separate small portions of tissue from the patient's body, and grasping or suction devices have been used to retrieve the tissue. For removal of small organs or tissue in laparoscopic or endoscopic surgical procedures, combination instruments that combine cutting and suction functions are known. Such dual function cutting/suction instruments can include a cutting instrument disposed inside a tube having a notch or other opening to permit the cutting instrument to have selective access to body tissue.
A single assembly that allows the irrigation, cutting, and suction functions to be carried out single-handedly by a surgeon would be highly desirable, and the cutter of the present invention may be incorporated into such a multifunction device. The cutter of the present invention may be used on any type of cannula-type device.
Notched cannulas having internally driven cutting tubes to cut tissue are known. For example, U.S. Pat. No. 4,099,529 to Peyman; U.S. Pat. Nos. 4,111,207 and 4,011,869 to Seiler, Jr.; U.S. Pat. No. 4,589,414 to Yoshida et al.; and U.S. Pat. No. 5,355,671 and U.S. Pat. application Ser. Nos. 07/830,580 and 08/060,423 to Clement and assigned to Mectra Labs, Inc. all describe surgical cutting instruments terminating in a cannula having a notch.
The present invention provides a surgical assembly for removal of body tissue. Preferably, the entire assembly is used a single time, and is constructed from low-cost, disposable materials. A preferred embodiment of the surgical assembly includes an outer cannula having an open distal end, a proximal end, and a side wall defining an interior region. During a surgical operation, the distal end of the cannula is inserted into a patient's body. A first notch is defined at the distal end of the cannula to permit access to the interior region. In practice, tissue is maneuvered into the notch prior to removal of the tissue from the body.
An annular blade is fixed to the distal end of the outer cannula and is arranged so that an annular gap is formed between the annular blade and the outer cannula. The annular blade has a proximal edge formed to include a cutting edge for cutting tissue received in the notch and the cutting edge is positioned to lie adjacent to the notch.
A hollow inner cannula is movably positioned in the interior region of the outer cannula. The inner cannula defines a cannula passageway, and a cutting edge for cutting tissue is provided on the inner cannula. The cutting edge is positioned to cut tissue that has entered the interior region of the outer cannula through the first notch. The cutting edge is additionally positioned to be received by the gap when the cutting edge is in the cutting position.
Means for removing the cut tissue from the inner cannula such as a vacuum source may be coupled to the inner cannula. This vacuum draws cut tissue out of the assembly and stores it in a storage chamber for later analysis. Means for supplying a saline solution for flow into the patient's body may also be coupled to the inner cannula if an irrigation feature is desired.
In summary, an improved cutting mechanism is provided by the use of an exterior and an interior concentric cannula that are arranged to form a gap adjacent to the notch in the exterior cannula. A hollow intermediate cannula having a cutting edge is arranged so that the cutting edge can be received within the gap. When tissue to be dissected is extended through the notch and across the gap, the passing of the intermediate cannula across the notch to the gap is effective for severing the tissue. The addition of the interior cannula provides a significant improvement in the effectiveness of the cutting tool.
According to the present invention, a surgical cutter for removal of body tissue during surgery is provided. The cutter includes a cannula having a proximal end and a distal end and a side wall defining an interior region. The distal end is positionable into a patient's body during surgery while the proximal end remains outside of the patient's body. The side wall is formed to include an orifice having a proximal edge and a distal edge and the orifice is arranged for receiving body tissue. Additionally, means for providing suction to the interior region may be included with the cutter.
A first annular wall is fixed to the distal end of the cannula. The first annular wall has a proximal edge. The wall is arranged to define an annular gap between the first annular wall and the side wall of the cannula.
An annular intermediate wall is also provided. The annular intermediate wall has an annular distal edge sized to be received by the gap. The annular intermediate wall and the cannula are arranged for relative axial movement between a first position with the intermediate wall remote from the orifice and a second position with the intermediate wall received in the gap to cut tissue received in the orifice.
In one version, the first annular wall is disposed within the interior region of the cannula. As a result, the gap and hence the annular intermediate wall are also positioned to lie within the interior region. In this version, the cannula is fixed to the cutter and the intermediate wall reciprocates inside of the cannula between the first position and the second position, though it will be apparent to one skilled in the art that the intermediate wall can be fixed and the cannula and first annular wall can reciprocate to achieve the same result. In a first embodiment the edges of the orifice are not cutting edges, however in a second embodiment, cutting edges are provided on the edges of the orifice.
In another embodiment, the first annular wall is disposed outside of the interior region of the cannula. As a result, the gap and hence the annular intermediate wall are also positioned to lie outside of the interior region. In this embodiment, the cannula is fixed to the cutter and the intermediate wall reciprocates outside of the cannula between the first position and the second position. Again, it will be apparent to one skilled in the art that the intermediate wall can be fixed and the cannula and first annular wall can reciprocate to achieve the same result.
Some preferred embodiments of this invention include a cannula with a distal end formed to include an aperture in fluid communication with the interior region. This aperture facilitates the introduction of carbon dioxide gas or saline solution into the patient's body, both of which are useful to the procedures for which the instrument is necessary. However, it will be apparent to one skilled in the art that whether the distal end of the cannula is open including an aperture or is closed with no aperture has no bearing on the performance of the tissue cutter of the present invention.
It has been found that to achieve the best tissue removal results, the cutting edges of the tissue cutter of the present invention can be formed using electrical discharge machining (EDM) and an electrical etching technique. EDM forms a surgically sharp edge on the cutting edge and is followed by the electrical etching process. The electrical etching process involves exposing the edge to a solution including phosphoric acid and sulfuric acid while the edge is at an electrical potential of approximately twelve volts D.C. The etching process alters the shape of the cutting edge resulting in a more effective instrument.
Other objects and advantages of the invention will become apparent from the following description of a preferred embodiment presently perceived as the best mode for practice of the invention and consideration of the accompanying drawings.